In general, when a gaze is tracked by using a face image of a user, a gaze vector is detected by using a lighting reflection point and a center of pupil. If the lighting reflection point and the center of pupil are calculated exactly, an exact gaze vector may be detected theoretically.
In a case of a method of detecting a gaze vector by using the lighting reflection point, a center point of cornea is obtained by using a crossing point of lines connecting lighting reflection points generated in a pupil by two infrared light emitting diodes (LEDs) to respective lightings. After a center of pupil is obtained by applying an image processing scheme to an image of an eyeball appearing at a camera, a gaze is calculated by using a vector connecting the center of pupil to a center point of cornea.
As mentioned above, in order to detect a gaze vector by using the lighting reflection point and the center of pupil, if the lighting reflection point and the center of the pupil are exactly detected, the gaze vector may be exactly calculated theoretically. However, in a case of the lighting reflection point, the lighting reflection point is spread in a direction of the eye. Alternatively, when a user wears spectacles, the lighting reflection point may be shielded due to light in the spectacles. In this case, the gaze vector cannot be calculated.